User equipment and evolved node-b and methods for operation in a coverage enhancement mode

ABSTRACT

Embodiments of a User Equipment (UE) and an Evolved Node-B (eNB) and methods for operating in a coverage enhancement (CE) mode are generally described herein. The UE may include hardware processing circuitry configured to determine a CE category for the UE based at least partly on downlink channel statistics related to reception of one or more downlink signals from an eNB. The CE category may reflect one of a level of additional link margin and a level of system resources for performance at or above a performance threshold. The hardware processing circuitry may be further configured to transmit, in physical random access channel (PRACH) frequency resources, a PRACH preamble according to an uplink access repetition number. The PRACH frequency resources and the uplink access repetition number may be based at least partly on CE category for the UE.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/898,425, filed Oct. 31, 2013, which is incorporated hereinby reference in its entirety.

TECHNICAL FIELD

Embodiments pertain to wireless communications. Some embodiments relateto wireless networks including LTE networks. Some embodiments relate tooperation in a coverage enhancement mode. Some embodiments relate toMachine Type Communication (MTC).

BACKGROUND

A mobile device operating in a cellular network may experienceperformance degradation in some cases, which may affect the ability ofthe device to connect or reconnect to the network. As an example, themobile device may lose coverage as it moves toward or beyond the edge ofa cell or sector of the network. As another example, a mobile device maybe expected to operate in an environment with low link quality. Devicesthat support Machine Type Communication (MTC), for instance, mayexchange small quantities of data at an infrequent rate in such low linkconditions.

In any case, connection or reconnection to the network may bechallenging in these and other scenarios. Accordingly, methods andtechniques for connection or reconnection to the network are needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional diagram of a 3GPP network in accordance with someembodiments;

FIG. 2 is a block diagram of a User Equipment (UE) in accordance withsome embodiments;

FIG. 3 is a block diagram of an Evolved Node-B (eNB) in accordance withsome embodiments;

FIG. 4 is an example of a scenario in which UEs operating in a networkmay experience reduced coverage from an eNB in accordance with someembodiments;

FIG. 5 illustrates the operation of a method of communicating on arandom access channel (RACH) in accordance with some embodiments;

FIG. 6 illustrates the operation of another method of communicating on aRACH in accordance with some embodiments;

FIG. 7 illustrates examples of MAC random access responses (RARs) inaccordance with some embodiments;

FIG. 8 illustrates a method for connection or reconnection in accordancewith some embodiments; and

FIG. 9 illustrates an example of a table of repetition levels inaccordance with some embodiments.

DETAILED DESCRIPTION

The following description and the drawings sufficiently illustratespecific embodiments to enable those skilled in the art to practicethem. Other embodiments may incorporate structural, logical, electrical,process, and other changes. Portions and features of some embodimentsmay be included in, or substituted for, those of other embodiments.Embodiments set forth in the claims encompass all available equivalentsof those claims

FIG. 1 shows a portion of an end-to-end network architecture of an LTEnetwork with various components of the network in accordance with someembodiments. The network 100 comprises a radio access network (RAN)(e.g., as depicted, the E-UTRAN or evolved universal terrestrial radioaccess network) 100 and the core network 120 (e.g., shown as an evolvedpacket core (EPC)) coupled together through an S1 interface 115. Forconvenience and brevity sake, only a portion of the core network 120, aswell as the RAN 100, is shown.

The core network 120 includes mobility management entity (MME) 122,serving gateway (serving GW) 124, and packet data network gateway (PDNGW) 126. The RAN 100 includes Evolved Node-B's (eNBs) 104 (which mayoperate as base stations) for communicating with User Equipment (UE)102. The eNBs 104 may include macro eNBs and low power (LP) eNBs.

The MME is similar in function to the control plane of legacy ServingGPRS Support Nodes (SGSN). The MME manages mobility aspects in accesssuch as gateway selection and tracking area list management. The servingGW 124 terminates the interface toward the RAN 100, and routes datapackets between the RAN 100 and the core network 120. In addition, itmay be a local mobility anchor point for inter-eNB handovers and alsomay provide an anchor for inter-3GPP mobility. Other responsibilitiesmay include lawful intercept, charging, and some policy enforcement. Theserving GW 124 and the MME 122 may be implemented in one physical nodeor separate physical nodes. The PDN GW 126 terminates an SGi interfacetoward the packet data network (PDN). The PDN GW 126 routes data packetsbetween the EPC 120 and the external PDN, and may be a key node forpolicy enforcement and charging data collection. It may also provide ananchor point for mobility with non-LTE accesses. The external PDN can beany kind of IP network, as well as an IP Multimedia Subsystem (IMS)domain. The PDN GW 126 and the serving GW 124 may be implemented in onephysical node or separated physical nodes.

The eNBs 104 (macro and micro) terminate the air interface protocol andmay be the first point of contact for a UE 102. In some embodiments, aneNB 104 may fulfill various logical functions for the RAN 100 includingbut not limited to RNC (radio network controller functions) such asradio bearer management, uplink and downlink dynamic radio resourcemanagement and data packet scheduling, and mobility management. Inaccordance with embodiments, UEs 102 may be configured to communicateOFDM communication signals with an eNB 104 over a multicarriercommunication channel in accordance with an OFDMA communicationtechnique. The OFDM signals may comprise a plurality of orthogonalsubcarriers.

In accordance with some embodiments, a UE 102 may transmit, forreception at an eNB 104, a physical random access channel (PRACH)preamble according to an uplink access repetition number. The UE 102 mayalso receive, from the eNB 104, a random access response (RAR) messageaccording to a downlink repetition number. These embodiments aredescribed in more detail below.

The S1 interface 115 is the interface that separates the RAN 100 and theEPC 120. It is split into two parts: the S1-U, which carries trafficdata between the eNBs 104 and the serving GW 124, and the S1-MME, whichis a signaling interface between the eNBs 104 and the MME 122. The X2interface is the interface between eNBs 104. The X2 interface comprisestwo parts, the X2-C and X2-U. The X2-C is the control plane interfacebetween the eNBs 104, while the X2-U is the user plane interface betweenthe eNBs 104.

With cellular networks, LP cells are typically used to extend coverageto indoor areas where outdoor signals do not reach well, or to addnetwork capacity in areas with very dense phone usage, such as trainstations. As used herein, the term low power (LP) eNB refers to anysuitable relatively low power eNB for implementing a narrower cell(narrower than a macro cell) such as a femtocell, a picocell, or a microcell. Femtocell eNBs are typically provided by a mobile network operatorto its residential or enterprise customers. A femtocell is typically thesize of a residential gateway or smaller, and generally connects to theuser's broadband line. Once plugged in, the femtocell connects to themobile operator's mobile network and provides extra coverage in a rangeof typically 30 to 50 meters for residential femtocells. Thus, a LP eNBmight be a femtocell eNB since it is coupled through the PDN GW 126Similarly, a picocell is a wireless communication system typicallycovering a small area, such as in-building (offices, shopping malls,train stations, etc.), or more recently in-aircraft. A picocell eNB cangenerally connect through the X2 link to another eNB such as a macro eNBthrough its base station controller (BSC) functionality. Thus, LP eNBmay be implemented with a picocell eNB since it is coupled to a macroeNB via an X2 interface. Picocell eNBs or other LP eNBs may incorporatesome or all functionality of a macro eNB. In some cases, this may bereferred to as an access point base station or enterprise femtocell.

In some embodiments, a downlink resource grid may be used for downlinktransmissions from an eNB 104 to a UE 102, while uplink transmissionfrom the UE 102 to the eNB 104 may utilize similar techniques. The gridmay be a time-frequency grid, called a resource grid or time-frequencyresource grid, which is the physical resource in the downlink in eachslot. Such a time-frequency plane representation is a common practicefor OFDM systems, which makes it intuitive for radio resourceallocation. Each column and each row of the resource grid correspond toone OFDM symbol and one OFDM subcarrier, respectively. The duration ofthe resource grid in the time domain corresponds to one slot in a radioframe. The smallest time-frequency unit in a resource grid is denoted asa resource element. Each resource grid comprises a number of resourceblocks, which describe the mapping of certain physical channels toresource elements. Each resource block comprises a collection ofresource elements and in the frequency domain, this represents thesmallest quanta of resources that currently can be allocated. There areseveral different physical downlink channels that are conveyed usingsuch resource blocks. With particular relevance to this disclosure, twoof these physical downlink channels are the physical downlink sharedchannel and the physical down link control channel.

The physical downlink shared channel (PDSCH) carries user data andhigher-layer signaling to a UE 102 (FIG. 1). The physical downlinkcontrol channel (PDCCH) carries information about the transport formatand resource allocations related to the PDSCH channel, among otherthings. It also informs the UE 102 about the transport format, resourceallocation, and H-ARQ information related to the uplink shared channel.Typically, downlink scheduling (assigning control and shared channelresource blocks to UEs 102 within a cell) is performed at the eNB 104based on channel quality information fed back from the UEs 102 to theeNB 104, and then the downlink resource assignment information is sentto a UE 102 on the control channel (PDCCH) used for (assigned to) the UE102.

The PDCCH uses CCEs (control channel elements) to convey the controlinformation. Before being mapped to resource elements, the PDCCHcomplex-valued symbols are first organized into quadruplets, which arethen permuted using a sub-block inter-leaver for rate matching. EachPDCCH is transmitted using one or more of these control channel elements(CCEs), where each CCE corresponds to nine sets of four physicalresource elements known as resource element groups (REGs). Four QPSKsymbols are mapped to each REG. The PDCCH can be transmitted using oneor more CCEs, depending on the size of DCI and the channel condition.There may be four or more different PDCCH formats defined in LTE withdifferent numbers of CCEs (e.g., aggregation level, L=1, 2, 4, or 8).

FIG. 2 shows a block diagram of a UE 200 in accordance with someembodiments, while FIG. 3 shows a block diagram of an eNB 300 inaccordance with some embodiments. It should be noted that in someembodiments, the eNB 300 may be a stationary non-mobile device. The UE200 may be a UE 102 as depicted in FIG. 1, while the eNB 300 may be aneNB 104 as depicted in FIG. 1. The UE 200 may include physical layercircuitry 202 for transmitting and receiving signals to and from the eNB300, other eNBs, other UEs or other devices using one or more antennas201, while the eNB 300 may include physical layer circuitry 302 fortransmitting and receiving signals to and from the UE 200, other eNBs,other UEs or other devices using one or more antennas 301. The UE 200may also include medium access control layer (MAC) circuitry 204 forcontrolling access to the wireless medium, while the eNB 300 may alsoinclude medium access control layer (MAC) circuitry 304 for controllingaccess to the wireless medium. The UE 200 may also include processingcircuitry 206 and memory 208 arranged to perform the operationsdescribed herein, and the eNB 300 may also include processing circuitry306 and memory 308 arranged to perform the operations described herein.

In some embodiments, mobile devices or other devices described hereinmay be part of a portable wireless communication device, such as apersonal digital assistant (PDA), a laptop or portable computer withwireless communication capability, a web tablet, a wireless telephone, asmartphone, a wireless headset, a pager, an instant messaging device, adigital camera, an access point, a television, a medical device (e.g., aheart rate monitor, a blood pressure monitor, etc.), or other devicethat may receive and/or transmit information wirelessly. In someembodiments, the mobile device or other device can be the UE 200 or theeNB 300 configured to operate in accordance with 3GPP standards. In someembodiments, the mobile device or other device may be configured tooperate according to other protocols or standards, including IEEE 802.11or other IEEE standards. In some embodiments, the mobile device or otherdevice may include one or more of a keyboard, a display, a non-volatilememory port, multiple antennas, a graphics processor, an applicationprocessor, speakers, and other mobile device elements. The display maybe an LCD screen including a touch screen.

The antennas 201, 301 may comprise one or more directional oromnidirectional antennas, including, for example, dipole antennas,monopole antennas, patch antennas, loop antennas, microstrip antennas orother types of antennas suitable for transmission of RF signals. In somemultiple-input multiple-output (MIMO) embodiments, the antennas 201, 301may be effectively separated to take advantage of spatial diversity andthe different channel characteristics that may result.

Although the UE 200 and eNB 300 are each illustrated as having severalseparate functional elements, one or more of the functional elements maybe combined and may be implemented by combinations ofsoftware-configured elements, such as processing elements includingdigital signal processors (DSPs), and/or other hardware elements. Forexample, some elements may comprise one or more microprocessors, DSPs,field-programmable gate arrays (FPGAs), application specific integratedcircuits (ASICs), radio-frequency integrated circuits (RFICs) andcombinations of various hardware and logic circuitry for performing atleast the functions described herein. In some embodiments, thefunctional elements may refer to one or more processes operating on oneor more processing elements.

Embodiments may be implemented in one or a combination of hardware,firmware and software. Embodiments may also be implemented asinstructions stored on a computer-readable storage device, which may beread and executed by at least one processor to perform the operationsdescribed herein. A computer-readable storage device may include anynon-transitory mechanism for storing information in a form readable by amachine (e.g., a computer). For example, a computer-readable storagedevice may include read-only memory (ROM), random-access memory (RAM),magnetic disk storage media, optical storage media, flash-memorydevices, and other storage devices and media. Some embodiments mayinclude one or more processors and may be configured with instructionsstored on a computer-readable storage device.

In accordance with embodiments, the UE 102 may determine a coverageenhancement (CE) category for the UE 102 based at least partly ondownlink channel statistics related to reception of one or more downlinksignals from the eNB 104. The CE category may reflect one of a level ofadditional link margin and a level of system resources for performanceat or above a performance threshold. The UE 102 may also transmit, inphysical random access channel (PRACH) frequency resources, a PRACHpreamble according to an uplink access repetition number. The PRACHfrequency resources and the uplink access repetition number may be basedat least partly on the CE category for the UE 102. These embodiments aredescribed in more detail below.

In some scenarios, the UE 102 operating in a cellular communicationnetwork (such as 100) may lose connectivity to the network or may havedifficulty in remaining connected to the network for various reasons. Asan example, the UE 102 may move toward an area with reduced coverage,such as the edge of a sector or cell. As another example, the UE 102 mayoperate in an area that is essentially out of the normal coverage of thenetwork, such as in a basement of a building. As another example, the UE102 or other device may support Machine Type Communication (MTC). MTCdevices or devices operating in an MTC mode may be expected to operatein highly challenging link budget scenarios while exchanging smallquantities of data at an infrequent rate.

Referring to FIG. 4, an example of a connection scenario 400 is shown,in which a tower eNB 405 (which can be the eNB 104) and three UEs 410,415, 420 (which can be the UE 102) located at various distances from theeNB 405 are operating, or attempting to operate, as part of a 3GPP orother network. It should be noted that the eNB 405 is not limited to thetower configuration and that scenarios described herein are not limitedto the number or distribution of eNBs 405 or UEs 410, 415, 420 as shownin FIG. 4. The first UE 410 is in communication with the eNB 405 overthe link 430, and is comfortably located within the coverage area 450 ofthe eNB 405. As such, it is expected that the first UE 410 may not beinvolved in a reconnection procedure. The second UE 415 is locatedoutside of the coverage area 450 in a demarcated zone 460, and may beattempting a reconnection procedure over the link 435 (note the link maynot actually be established or stable yet). Similarly, the third UE 420is also located outside of the coverage area 450 in another demarcatedzone 470 that is further away from the eNB 405 than the first demarcatedzone 460. The third UE 420 may also be attempting a reconnectionprocedure over the link 440 (which may not actually be established orstable yet).

The second UE 415 and third UE 420 may be described as needing “coverageenhancement,” or operating in “coverage enhancement mode,” as they areout of the coverage area 450. Additionally, while both UEs 415, 420 areoutside of the coverage area 450, the third UE 420 may have more troubleor challenges in reconnecting than would the second UE 415, as the thirdUE 420 is further away from the eNB 405. Accordingly, it may be possibleto formulate different categories of coverage enhancement for UEsdepending on how far out of coverage they are located or other factors.In some embodiments, descriptions may be used in the categories. Forinstance, the third UE 420 may be considered in a “high” category ofcoverage enhancement mode while the second UE 415 may be considered in a“low” category of coverage enhancement mode. In some embodiments, thecategories may be numerical, such as 5 dB, 10 dB, and 15 dB, which mayrepresent an additional amount of link budget that may be added to theUEs 415, 420 in order to realize a “normal operation.” The normaloperation may be characterized by any suitable criteria such as a targetpacket error rate, acquisition time, data throughput or the like.

It should be pointed out that the above discussion focuses on path lossdue to distance only, for purposes of illustration, but this is notlimiting. It is known in the art that path loss, signal loss, coverageholes or the like may result from effects other than distance, such asobstacles or indoor location. For instance, a device located in abasement of a building close to the eNB 405 may actually be in need of acoverage enhancement while another device located much further away, butoutdoors, may have a stronger connection to the eNB 405 and may be inneed of less or no coverage enhancement.

Referring to FIG. 5, a method 500 of operating in accordance with acoverage enhancement mode is shown. It is important to note thatembodiments of the method 500 may include additional or even feweroperations or processes in comparison to what is illustrated in FIG. 5.In addition, embodiments of the method 500 are not necessarily limitedto the chronological order that is shown in FIG. 5. In describing themethod 500, reference may be made to FIGS. 1-4 and 6-9, although it isunderstood that the method 500 may be practiced with any other suitablesystems, interfaces and components. For example, reference may be madeto the scenario 400 in FIG. 4 described earlier for illustrativepurposes, but the techniques and operations of the method 500 are not solimited.

In addition, while the method 500 and other methods described herein mayrefer to eNBs 104 or UEs 102 operating in accordance with 3GPP or otherstandards, embodiments of those methods are not limited to just thoseeNBs 104 or UEs 102 and may also be practiced on other mobile devices,such as a Wi-Fi access point (AP) or user station (STA). Moreover, themethod 500 and other methods described herein may be practiced bywireless devices configured to operate in other suitable types ofwireless communication systems, including systems configured to operateaccording to various IEEE standards such as IEEE 802.11. In addition themethod 500 and other methods described herein may be practiced by UEs orother devices that support or are configured to support Machine TypeCommunication (MTC) operation.

At operation 505 of the method 500, a coverage enhancement (CE) categorymay be determined for the UE 102. The CE category for the UE 102 mayreflect one of a level of additional link margin and a level of systemresources for performance at or above a performance threshold associatedwith a normal operating mode for the UE 102. In some embodiments, the CEcategory may be determined from a group of candidate CE categories. Asan example, the candidate CE categories may include 5, 10 or 15 dB,which may refer to a link budget addition that may enable a level ofperformance for the UE 102 in terms of error rate, throughput or otherperformance measure. An additional CE category may include “no CE” orsimilar, which may reflect that the UE 102 is not operating in a CEmode. In addition, previously described examples related to CEcategories may also be used, such as “high” and “low.”

The determination of the CE category may be based at least partly ondownlink channel statistics related to reception of one or more downlinksignals at the UE from an Evolved Node-B (eNB). In some embodiments, thedownlink channel statistics may include reference signal received power(RSRP) or other path loss measurements at the UE. As an example, adetermined path loss at the UE 102 may be compared with a predeterminedlink budget path loss to determine the CE category for the UE 102. Thepredetermined link budget path loss may indicate a maximum path loss for“normal” operation in terms of packet error rate or other measure. Thestatistics may be based on or collected over any suitable time period,which may be on the order of symbol periods, sub-frames, seconds,minutes or longer. The measurements may include averages, movingaverages, weighted averages or other suitable statistics, and may referto scalar or logarithmic (dB) quantities.

At operation 510, a PRACH preamble may be transmitted in PRACH frequencyresources according to an uplink access repetition number. The PRACHfrequency resources may be based at least partly on the CE category forthe UE 102. In some embodiments, the group of candidate CE categoriesmay include a first and a second candidate CE category for which PRACHfrequency resources for the first CE category are exclusive to PRACHfrequency resources for the second CE category. In addition, the groupof candidate CE categories may include more than the first and secondcandidate CE categories, and some or all of the candidate CE categoriesmay be associated with different PRACH frequency resources that may beexclusive to each other. Accordingly, the frequency resources used forthe transmission of the PRACH preamble may indicate or reflect thedetermined CE category for the UE 102. Mappings or assignments of PRACHfrequency resources to candidate CE categories may be predetermined, maybe part of 3GPP or other standards or may be determined by the network.In addition, the PRACH frequency resources used by the UE 102 whenoperating in the CE mode may be disjoint from PRACH frequency resourcesused by UEs not operating in the CE mode.

In some embodiments, a random access radio network temporary identifier(RA-RNTI) computed for the PRACH preamble transmission may depend onwhether or not the UE 102 is in the CE mode. As an example, the RA-RNTImay be computed as (1+t_id+10*f id+c*MTC_id), in which t_id is the indexof the first sub-frame of the specified PRACH preamble, f_id is theindex of the specified PRACH preamble within that sub-frame, the valueof “c” may be 60, and the MTC_id is 0 or 1 when the UE 102 is not, oris, in the CE mode.

The uplink access repetition number may be based at least partly on theCE category for the UE 102. In some embodiments, the group of candidateCE categories may include a first and a second candidate CE category forwhich an uplink access repetition number for the first CE category isdifferent from an uplink access repetition number for the second CEcategory. The uplink access repetition number may refer to a number ofrepetitions of the PRACH preamble to be transmitted by the UE 102. Inaddition, the group of candidate CE categories may include more than thefirst and second candidate CE categories, and some or all of thecandidate CE categories may be associated with uplink access repetitionnumbers that may be different. In some embodiments, an uplink accessrepetition number (or other repetition numbers or levels describedherein) for a CE category considered “high” may be larger than an uplinkaccess repetition number for a CE category considered “low.” Forinstance, the UE 102 may repeat the PRACH preamble 100 times whenoperating in the CE category of 15 dB and may repeat the PRACH preambleonly 20 times when operating in the CE category of 5 dB. Accordingly,the larger number of repetitions may provide additional diversity orenergy gain for the UE 102 when it operates in a higher CE category. Thenumber of repetitions for the candidate CE categories may bepre-determined through simulation or analysis or other techniques. Insome embodiments, the repetitions of the PRACH preamble may betransmitted during different time periods.

At operation 515 of the method 500, a Random Access Response (RAR) maybe received from the eNB 104 according to a downlink repetition number.As previously described, the PRACH frequency resources used by the UE102 may indicate the determined CE category for the UE 102, which may beascertained by the eNB 104 using knowledge of the previously describedmappings and assignments between PRACH frequency resources and CEcategories. The downlink repetition number may refer to a number ofrepetitions of the RAR to be transmitted by the eNB 104, and the numberof repetitions for some or all of the candidate CE categories may bedifferent. Accordingly, the downlink repetition number may be based atleast partly on the CE category for the UE 102, and may bepre-determined through simulation or analysis or other techniques.

In some embodiments, the downlink repetition number may be included in aPDCCH. A new downlink control information (DCI) format, or an existingDCI format such as “1A” or other in 3GPP standards, may include thedownlink repetition number or an indicator of it. As an example, thedownlink repetition number may include a bit field of two bitscorresponding to “no repetition” and repetition levels of 0, 1, and 2,in which the number of repetitions associated with each repetition levelmay be pre-defined or signaled in other messages. As another example,the downlink repetition number may be a single bit corresponding to “norepetition” or repetition according to a pre-defined or previouslysignaled repetition number. As another example, the downlink repetitionnumber may be a bit field that explicitly states a number of repetitionsto be used. Embodiments are not limited to the number of bits or levelsdescribed in the above examples, however, as the downlink repetitionnumber may describe or specify the amount of repetition in any suitablemanner. In some embodiments, the downlink repetition number may refer toa “PDSCH repetition level” as will be described later.

In some embodiments, the RAR may be received on PDSCH frequencyresources that are based at least partly on the CE category for the UE102. In addition, the PDSCH frequency resources for the RAR may bedisjoint from PDSCH frequency resources used for RARs or other messagesfor UEs not operating in the CE mode. In some embodiments, a pre-definedfrequency allocation for the PDSCH may be determined Accordingly, thePDCCH may not need to be decoded at the UE 102, which may be beneficialdue to the fact that a large number of repetitions of the PDCCH may haveto be used when the UE 102 operates in the CE mode. That is, the UE 102may refrain from decoding the PDCCH as part of the reception of the RAR.Such an arrangement may be considered “PDCCH-less” operation.

In some embodiments, dedicated PDSCH frequency resources may bepre-defined and configured appropriately for coverage-limited MTC UEs.In addition, knowledge of a fixed timing relationship between PRACHtransmission and RAR reception may be used at the UE 102. Knowledge of atransport format for PDSCH transmission may also be used at the UE 102.In some embodiments, a control message, such as an SIB-2 or other SystemInformation Block (SIB) message, may include information such as thetiming relationship or transport format just described. The controlmessage may be transmitted to the UE 102 by the eNB 104, either as adedicated or broadcast message. In addition, information such as thetiming relationship or transport format just described may also bepre-defined in some embodiments.

At operation 520, an uplink control message may be transmitted on PUSCHresources according to an uplink control repetition number. Thetransmission may be in response to the reception of the RAR at the UE102. In some embodiments, the uplink control message may be an “L2/L3”message or may include or be included in one or more L2/L3 messages.

The uplink control repetition number may refer to a number ofrepetitions of the uplink control message to be transmitted by the UE102, and the number of repetitions for some or all of the candidate CEcategories may be different. In some embodiments, the uplink controlrepetition number may be based at least partly on the CE category forthe UE 102, and may be pre-determined through simulation or analysis orother techniques. In some embodiments, the uplink control repetitionnumber may be included in the RAR message received at the UE 102 atoperation 515. In some embodiments, the uplink control repetition numbermay be included in RAR content of the RAR message or may be included inan uplink grant included in the RAR message, as will be described inmore detail regarding the method 600 and FIG. 7. In addition, the uplinkcontrol repetition number may be a “PUSCH repetition level” that refersto a repetition number to be used for PUSCH transmission.

The uplink control message may be transmitted on PUSCH frequencyresources that are based at least partly on the CE category for the UE102. In addition, the PUSCH frequency resources for the uplink controlmessage may be disjoint from PUSCH frequency resources used for uplinkcontrol or other messages for UEs not operating in the CE mode.

In some embodiments, the uplink control message may include a second CEcategory for the UE 102, which may be determined at the UE 102 based atleast partly on the reception of the RAR at operation 515. For instance,based on a signal quality, signal level or other measurement for thereception of the RAR, the UE 102 may select a second CE category for theUE 102. The second category may be selected from a second group ofcandidate CE categories that may or may not be different from the groupof candidate CE categories used in other operations such as 505-520. Forinstance, the second group of candidate CE categories may cover a largerrange or provide finer granularity. Accordingly, the second CE categorymay be a new or refined value that may provide more information to theeNB 104 about coverage enhancement for the UE 102.

At operation 525, a contention resolution message may be received fromthe eNB according to the downlink repetition number. In someembodiments, the downlink repetition numbers for operations 515 and 525may be the same. However, this arrangement is not limiting, and the twonumbers may be different in some embodiments. As previously described,the downlink repetition number used at operation 525 may refer to anumber of repetitions of the contention resolution message transmittedby the eNB 104, and the number of repetitions for some or all of thecandidate CE categories may be different. In some embodiments, thedownlink repetition number used at operation 525 may be based at leastpartly on the CE category for the UE 102, and may be pre-determinedthrough simulation or analysis or other techniques.

Referring to FIG. 6, a method 600 of operating in a coverage enhancementmode is shown. As mentioned previously regarding the method 500,embodiments of the method 600 may include additional or even feweroperations or processes in comparison to what is illustrated in FIG. 6and embodiments of the method 600 are not necessarily limited to thechronological order that is shown in FIG. 6. In describing the method600, reference may be made to FIGS. 1-5 and 7-9, although it isunderstood that the method 600 may be practiced with any other suitablesystems, interfaces and components. For example, reference may be madeto the scenario 400 in FIG. 4 described earlier for illustrativepurposes, but the techniques and operations of the method 600 are not solimited. In addition, embodiments of the method 600 may refer to eNBs104, UEs 102, APs, STAs or other wireless or mobile devices.

It should be noted that the method 600 may be practiced at the eNB 104,and may include exchanging of signals or messages with the UE 102.Similarly, the method 500 may be practiced at the UE 102, and mayinclude exchanging of signals or messages with the eNB 104. In somecases, operations and techniques described as part of the method 500 maybe relevant to the method 600. For instance, an operation of the method500 may include transmission of a message by the UE 102 while anoperation of the method 600 may include reception of the same message atthe eNB 104.

At operation 605 of the method 600, a PRACH preamble may be received atthe eNB 104 from the UE 102 operating in a coverage enhancement (CE)mode on PRACH frequency resources. The PRACH preamble may be receivedaccording to an uplink access repetition number, which may refer to anumber of repetitions of the PRACH preamble transmitted by the UE 102.In some embodiments, uplink access repetition numbers may be based atleast partly on a CE category for the UE, which may be selected from agroup of candidate CE categories, as previously described. The uplinkaccess repetition numbers for the CE categories may be different and mayalso be known at the eNB 104 for use in the reception of the PRACH atoperation 605.

At operation 610, a CE category may be determined for the UE 102 from agroup of candidate CE categories, and the determination may be based atleast partly on the PRACH frequency resources used for the PRACHpreamble. As previously described, some or all of the candidate CEcategories may be associated with different PRACH frequency resourcesthat may be exclusive to each other. Mappings or assignments of PRACHfrequency resources to candidate CE categories may be known at the eNB104. Accordingly, the eNB 104 may determine the CE category for the UE102 based on which PRACH frequency resources are used. In someembodiments, the PRACH frequency resources used by the UE 102 whenoperating in the CE mode may be disjoint from PRACH frequency resourcesused by UEs not operating in the CE mode.

At operation 615, a Random Access Response (RAR) may be transmittedaccording to a downlink repetition number, which may be based at leastpartly on the CE category for the UE 102. In some embodiments, PDSCHfrequency resources that are based at least partly on the CE categoryfor the UE 102 may be used for transmission of the RAR, and the PDSCHfrequency resources may be disjoint from second PDSCH frequencyresources for UEs not operating in a CE mode. In some embodiments, theRAR message may be transmitted in response to the reception of the PRACHpreamble at operation 605.

A physical downlink control channel (PDCCH) data block that includesPDSCH resource allocations for UEs not operating in the CE mode may betransmitted. In addition, the eNB 104 may refrain from transmission ofPDCCH data blocks for UEs operating in the CE mode. Accordingly, UEsoperating in the CE mode may receive the RAR on pre-determined PDSCHfrequency resources. Such an arrangement may be considered “PDCCH-less”operation, as the UEs operating in the CE mode may receive the RAR (orother messages) on PDSCH resources without decoding a PDCCH data block.

In addition, a control message may also be transmitted by the eNB 104for reception at the UE 102 that may include an allocation for the PDSCHfrequency resources. The control message may also include otherinformation, such as a modulation and coding scheme (MCS) indicator forthe RAR transmission. The MCS indicator may be an index that refers toan MCS of a group of pre-determined candidate MCSs, and each candidateMCS may refer to a modulation type (such as BPSK, QPSK, QAM or other)and a forward error correction (FEC) coding rate. A timing relationshipbetween PRACH transmission at the UE 102 and the RAR transmission mayalso be included in the control message. In some embodiments, the timingrelationship may be fixed. In some embodiments, the control message maybe an SIB-2 or other System Information Block (SIB) message of 3GPP orother standards.

At operation 620, an uplink control message may be received from the UE102 on PUSCH resources according to an uplink control repetition number.In some embodiments, the uplink control repetition number may be basedat least partly on the CE category for the UE 102, and may also bepredetermined In some embodiments, the RAR transmitted at operation 615(or another message from the eNB 104) may include the uplink controlrepetition number for the UE 102 to use. The value transmitted in theRAR may override or replace, in some cases, a predetermined value forthe uplink control repetition number that the UE may otherwise use, suchas a value based on the CE category as described above.

PUSCH frequency resources that are at least partly based on the CEcategory for the UE 102 may be used for reception of the uplink controlmessage at the eNB 104, and the PUSCH frequency resources may bedisjoint from second PUSCH frequency resources for UEs not operating ina CE mode.

At operation 625, a contention resolution message may be transmittedaccording to the downlink repetition number. As previously described,the downlink repetition number may be based at least partly on the CEcategory for the UE 102. In addition, the downlink repetition numberused at operation 625 may be the same as the downlink repetition numberused at operation 615, but is not limited as such. In some embodiments,PDSCH frequency resources that are at least partly based on the CEcategory for the UE 102 may be used for transmission of the contentionresolution message. The PDSCH frequency resources may or may not overlapthe PDSCH frequency resources used at operation 615 for transmission ofthe RAR.

At operation 630 of the method 600, a second PRACH preamble may bereceived from a second UE not operating in the CE mode. The second PRACHpreamble may be received on second PRACH frequency resources allocatedfor UEs that are not operating in the CE mode. In some embodiments, thesecond PRACH frequency resources may be exclusive to the PRACH frequencyresources allocated for UEs operating in the CE mode. It should also bepointed out that UEs not operating in the CE mode may include legacy UEsthat do not support coverage enhancement.

Referring to FIG. 7, examples of RAR messages, or MAC RAR messages, areshown in accordance with some embodiments. The RAR message 705 mayinclude other parameters or information 710 that may or may not berelated to coverage enhancement or connection or reconnectionoperations. The RAR message 705 may also include an uplink grant 715,which may include a PUSCH repetition level 725 and other parameters orinformation 720 that may or may not be related to coverage enhancementor connection or reconnection operations. As will be explained below,the PUSCH repetition level 725 may be the same as or may play the samerole as the uplink control repetition level previously described inrelation to methods 500 and 600.

Another example RAR 755 may include other parameters or information 760that may or may not be related to coverage enhancement or connection orreconnection operations. The RAR 755 may also include an uplink grant765 and a PUSCH repetition level 770. Accordingly, the PUSCH repetitionlevel 770 may be external to the uplink grant 765, in contrast to thePUSCH repetition level 725 which may be included in the uplink grant715.

In some embodiments, the PUSCH repetition level 725 may be included aspart of the RAR 705 transmitted by the eNB 104 at operation 615, or maybe included as part of the RAR 705 received at the UE 102 at operation515. In some embodiments, the PUSCH repetition level 770 may be includedas part of the RAR 755 transmitted by the eNB 104 at operation 615, ormay be included as part of the RAR 755 received at the UE 102 atoperation 515. It should be pointed out that the RARs 705, 755 serve toillustrate the concept of an RAR, but are not limiting, and othersuitable arrangements for the RAR may be used.

Referring to FIG. 8, a signal flow diagram illustrates an example of amethod 800 for connection or reconnection between the UE 102 and the eNB104. It should be noted that some of the operations of the method 800may be similar to operations included in the methods 500 or 600. In suchcases, descriptions of such operations in the methods 500 or 600 may beapplicable to corresponding operations included in the method 800. Inaddition, the method 800 shown in FIG. 8 may serve to illustrate theconcept of a connection or reconnection procedure, but it is notlimiting. Fewer or additional operations may be included in otherembodiments of connection or reconnection methods, and the chronologicalorder of operations is not limited to that shown in FIG. 8.

At operation 805, a PRACH preamble may be transmitted from the UE 102 tothe eNB 104 according to an uplink access repetition number. Atoperation 810, the eNB 104 may transmit a random access response (RAR)to the UE 102 according to a downlink repetition number. At operation815, the UE 102 may adjust its uplink timing. It should be noted thatthe UE 102 may perform operations 805 without timing synchronizationwith the eNB 104, and may acquire or refine its timing during thereception of the RAR at operation 810. At operation 820, the UE 102 maytransmit an uplink control message (such as an L2/L3 message) to the eNB104 according to an uplink control repetition number. At operation 825,the eNB 104 may transmit a contention resolution message to the UE 102according to the same downlink repetition number used at operation 810.

As previously described, repetition numbers may quantify how manyrepetitions of a message, such as the PRACH preamble or RAR, may betransmitted, and may depend on the CE category of the UE 102. Forinstance, the uplink access repetition number may refer to a number ofrepetitions of the PRACH preamble. For a connection or reconnectionprocedure, messages exchanged between the UE 102 and eNB 104 may berepeated according to predetermined values, which may be determinedthrough simulation or analysis. In some embodiments, a table may includerepetition values for different CE categories, and may be used inoperations described previously.

An example of such a table 900 is shown in FIG. 9. The column 910includes three CE categories 912, 914, 916, which correspond to 5, 10,and 15 dB in this example. The row associated with each of the three CEcategories 912, 914, 916 may include repetition values for use when theUE 102 operates in that particular CE category. The values for thecolumns 920, 930, 940, 950 may correspond to PRACH repetition level 920,(E)PDCCH repetition level 930, PDSCH repetition level 940, and PUSCHrepetition level 950. These labels on columns 920, 930, 940, 950 may bethe same as or related to repetition values previously described. As anexample, the PRACH repetition level 920 may be the same as or related tothe uplink access repetition number. As another example, the PDCCHrepetition level 930 or the PDSCH repetition level 940 may be the sameas or related to the downlink repetition number. As another example, thePUSCH repetition level 950 may be the same as or related to the uplinkcontrol repetition number.

A User Equipment (UE) to operate in accordance with a coverageenhancement (CE) mode is disclosed herein. The UE may include hardwareprocessing circuitry configured to determine, from a group of candidateCE categories, a CE category for the UE based at least partly ondownlink channel statistics related to reception of one or more downlinksignals at the UE from an Evolved Node-B (eNB). The hardware processingcircuitry may be further configured to transmit, in physical randomaccess channel (PRACH) frequency resources, a PRACH preamble accordingto an uplink access repetition number. In some embodiments, the PRACHfrequency resources and the uplink access repetition number may be basedat least partly on the CE category for the UE. In some embodiments, theCE category for the UE may reflect one of a level of additional linkmargin and a level of system resources for performance at or above aperformance threshold associated with a normal operating mode for theUE. In some embodiments, the downlink channel statistics may includereference signal received power (RSRP) or path loss measurements at theUE.

In some embodiments, the group of candidate CE categories may include afirst and a second candidate CE category for which an uplink accessrepetition number for the first CE category is different from an uplinkaccess repetition number for the second CE category. In someembodiments, the group of candidate CE categories may include a firstand a second candidate CE category for which PRACH frequency resourcesfor the first CE category are exclusive to PRACH frequency resources forthe second CE category.

The hardware processing circuitry may be further configured to receive,from the eNB, a Random Access Response (RAR) according to a downlinkrepetition number that is based at least partly on the CE category forthe UE. In some embodiments, the RAR may be received on physicaldownlink shared channel (PDSCH) frequency resources that may be based atleast partly on the CE category for the UE and the PDSCH frequencyresources may be disjoint from second PDSCH frequency resources for UEsnot operating in the CE mode. The hardware processing circuitry may befurther configured to receive, from the eNB, a physical downlink controlchannel (PDCCH) data block on PDCCH frequency resources for UEsoperating in the CE mode. In some embodiments, the PDCCH data block mayinclude a downlink control information (DCI) block that includes thedownlink repetition number. The hardware processing circuitry may befurther configured to refrain from decoding physical downlink controlchannel (PDCCH) data blocks as part of the reception of the RAR.

The hardware processing circuitry may be further configured to transmit,in response to the reception of the RAR, an uplink control message onphysical uplink shared channel (PUSCH) resources according to an uplinkcontrol repetition number. In some embodiments, the RAR may include theuplink control repetition number. In some embodiments, the RAR mayinclude an uplink grant for the UE and the uplink grant may include theuplink control repetition number. In some embodiments, the uplinkcontrol message may include a second CE category for the UE, the secondCE category may be selected from a second group of candidate CEcategories, and the second CE category may be determined at least partlyfrom the reception of the RAR. The hardware processing circuitry may befurther configured to receive, from the eNB, a contention resolutionmessage according to the downlink repetition number. In someembodiments, the UE may further support Machine Type Communication(MTC). In some embodiments, the UE may operate according to a 3GPPprotocol.

A non-transitory computer-readable storage medium that storesinstructions for execution by one or more processors to performoperations for communication by a User Equipment (UE) in a coverageenhancement mode is disclosed herein. The operations may configure theone or more processors to determine, from a group of candidate CEcategories, a CE category for the UE based at least partly on downlinkchannel statistics related to reception of one or more downlink signalsat the UE from an Evolved Node-B (eNB) and transmit, in physical randomaccess channel (PRACH) frequency resources, a PRACH preamble accordingto an uplink access repetition number. In some embodiments, the PRACHfrequency resources and the uplink access repetition number may be basedat least partly on the CE category for the UE. The operations mayfurther configure the one or more processors to receive, from the eNB, aRandom Access Response (RAR) according to a downlink repetition numberthat is based at least partly on the CE category for the UE. Theoperations may further configure the one or more processors to transmit,in response to the reception of the RAR, an uplink control message onphysical uplink shared channel (PUSCH) resources according to an uplinkcontrol repetition number that is based at least partly on the CEcategory for the UE.

A method for communicating in a coverage enhancement mode performed byUser Equipment (UE) is disclosed herein. The method may includedetermining, from a group of candidate CE categories, a CE category forthe UE based at least partly on downlink channel statistics related toreception of one or more downlink signals at the UE from an EvolvedNode-B (eNB). The method may further include transmitting, in physicalrandom access channel (PRACH) frequency resources, a PRACH preambleaccording to an uplink access repetition number. In some embodiments,the PRACH frequency resources and the uplink access repetition numberare based at least partly on the CE category for the UE. The method mayfurther include receiving, from the eNB, a Random Access Response (RAR)according to a downlink repetition number that is based at least partlyon the CE category for the UE. The method may further includetransmitting, in response to the reception of the RAR, an uplink controlmessage on physical uplink shared channel (PUSCH) resources according toan uplink control repetition number that is based at least partly on theCE category for the UE.

An Evolved Node-B (eNB) to operate in accordance with a coverageenhancement (CE) mode is disclosed herein. The eNB may include hardwareprocessing circuitry configured to receive, from a User Equipment (UE)operating in the CE mode, a physical random access channel (PRACH)preamble on PRACH frequency resources allocated for UEs operating in theCE mode. The hardware processing circuitry may be further configured todetermine, based at least partly on the PRACH frequency resources usedfor the reception of the PRACH preamble, a CE category for the UE from agroup of candidate CE categories and transmit a Random Access Response(RAR) according to a downlink repetition number that is based at leastpartly on the CE category for the UE. In some embodiments, the group ofcandidate CE categories may include a first and a second candidate CEcategory for which PRACH frequency resources for the first and second CEcategories are exclusive. In some embodiments, the RAR may betransmitted on physical downlink shared channel (PDSCH) frequencyresources that are based at least partly on the CE category for the UEand the PDSCH frequency resources may be disjoint from second PDSCHfrequency resources for UEs not operating in a CE mode.

The hardware processing circuitry may be further configured to transmita physical downlink control channel (PDCCH) data block that includesPDSCH resource allocations for UEs not operating in the CE mode and torefrain from transmission of PDCCH data blocks for UEs operating in theCE mode. The hardware processing circuitry may be further configured totransmit a control message that includes an allocation for the PDSCHfrequency resources, a modulation and coding scheme (MCS) indicator forthe RAR transmission, and a timing relationship between PRACHtransmission at the UE and the RAR transmission.

The hardware processing circuitry may be further configured to receive,from the UE, an uplink control message on physical uplink shared channel(PUSCH) resources according to an uplink control repetition number. Insome embodiments, the uplink control repetition number may be based atleast partly on the CE category for the UE. In some embodiments, the RARmay include the uplink control repetition number. The hardwareprocessing circuitry may be further configured to transmit, in responseto the reception of the uplink control message, a contention resolutionmessage according to the downlink repetition number. The hardwareprocessing circuitry may be further configured to receive, from a secondUE not operating in the CE mode, a second PRACH preamble on second PRACHfrequency resources allocated for UEs that are not operating in the CEmode. In some embodiments, the second PRACH frequency resources may beexclusive to the PRACH frequency resources allocated for UEs operatingin the CE mode. In some embodiments, the eNB may operate according to a3GPP protocol.

The Abstract is provided to comply with 37 C.F.R. Section 1.72(b)requiring an abstract that will allow the reader to ascertain the natureand gist of the technical disclosure. It is submitted with theunderstanding that it will not be used to limit or interpret the scopeor meaning of the claims The following claims are hereby incorporatedinto the detailed description, with each claim standing on its own as aseparate embodiment.

What is claimed is:
 1. A User Equipment (UE) to operate in accordancewith a coverage enhancement (CE) mode, the UE comprising hardwareprocessing circuitry configured to: determine, from a group of candidateCE categories, a CE category for the UE based at least partly ondownlink channel statistics related to reception of one or more downlinksignals at the UE from an Evolved Node-B (eNB); and transmit, inphysical random access channel (PRACH) frequency resources, a PRACHpreamble according to an uplink access repetition number; wherein thePRACH frequency resources and the uplink access repetition number arebased at least partly on the CE category for the UE.
 2. The UE accordingto claim 1, wherein the CE category for the UE reflects one of a levelof additional link margin and a level of system resources forperformance at or above a performance threshold associated with a normaloperating mode for the UE.
 3. The UE according to claim 1, wherein thedownlink channel statistics include reference signal received power(RSRP) or path loss measurements at the UE.
 4. The UE according to claim1, wherein the group of candidate CE categories includes a first and asecond candidate CE category for which an uplink access repetitionnumber for the first CE category is different from an uplink accessrepetition number for the second CE category and PRACH frequencyresources for the first CE category are exclusive to PRACH frequencyresources for the second CE category.
 5. The UE according to claim 1,the hardware processing circuitry further configured to receive, fromthe eNB, a Random Access Response (RAR) according to a downlinkrepetition number that is based at least partly on the CE category forthe UE.
 6. The UE according to claim 5, wherein: the RAR is received onphysical downlink shared channel (PDSCH) frequency resources that arebased at least partly on the CE category for the UE; and the PDSCHfrequency resources are disjoint from second PDSCH frequency resourcesfor UEs not operating in the CE mode.
 7. The UE according to claim 6,wherein: the hardware processing circuitry is further configured toreceive, from the eNB, a physical downlink control channel (PDCCH) datablock on PDCCH frequency resources for UEs operating in the CE mode; thePDCCH data block includes a downlink control information (DCI) blockthat includes the downlink repetition number.
 8. The UE according toclaim 6, wherein the hardware processing circuitry is further configuredto refrain from decoding physical downlink control channel (PDCCH) datablocks as part of the reception of the RAR.
 9. The UE according to claim5, the hardware processing circuitry further configured to transmit, inresponse to the reception of the RAR, an uplink control message onphysical uplink shared channel (PUSCH) resources according to an uplinkcontrol repetition number.
 10. The UE according to claim 9, wherein theRAR includes the uplink control repetition number.
 11. The UE accordingto claim 10, wherein the RAR includes an uplink grant for the UE and theuplink grant includes the uplink control repetition number.
 12. The UEaccording to claim 9, wherein: the uplink control message includes asecond CE category for the UE; the second CE category is selected from asecond group of candidate CE categories; and the second CE category isdetermined at least partly from the reception of the RAR.
 13. The UEaccording to claim 9, the hardware processing circuitry furtherconfigured to receive, from the eNB, a contention resolution messageaccording to the downlink repetition number.
 14. The UE according toclaim 1, wherein the UE is further to support Machine Type Communication(MTC) and to operate according to a 3GPP protocol.
 15. A non-transitorycomputer-readable storage medium that stores instructions for executionby one or more processors to perform operations for communication byUser Equipment (UE) in a coverage enhancement (CE) mode, the operationsto configure the one or more processors to: determine, from a group ofcandidate CE categories, a CE category for the UE based at least partlyon downlink channel statistics related to reception of one or moredownlink signals at the UE from an Evolved Node-B (eNB); and transmit,in physical random access channel (PRACH) frequency resources, a PRACHpreamble according to an uplink access repetition number; wherein thePRACH frequency resources and the uplink access repetition number arebased at least partly on the CE category for the UE.
 16. Thenon-transitory computer-readable storage medium according to claim 15,the operations to further configure the one or more processors toreceive, from the eNB, a Random Access Response (RAR) according to adownlink repetition number that is based at least partly on the CEcategory for the UE.
 17. The non-transitory computer-readable storagemedium according to claim 16, the operations to further configure theone or more processors to transmit, in response to the reception of theRAR, an uplink control message on physical uplink shared channel (PUSCH)resources according to an uplink control repetition number that is basedat least partly on the CE category for the UE.
 18. A method forcommunicating in a coverage enhancement (CE) mode performed by UserEquipment (UE), the method comprising: determining, from a group ofcandidate CE categories, a CE category for the UE based at least partlyon downlink channel statistics related to reception of one or moredownlink signals at the UE from an Evolved Node-B (eNB); andtransmitting, in physical random access channel (PRACH) frequencyresources, a PRACH preamble according to an uplink access repetitionnumber; wherein the PRACH frequency resources and the uplink accessrepetition number are based at least partly on the CE category for theUE.
 19. The method according to claim 18, further comprising receiving,from the eNB, a Random Access Response (RAR) according to a downlinkrepetition number that is based at least partly on the CE category forthe UE.
 20. An Evolved Node-B (eNB) to operate in accordance with acoverage enhancement (CE) mode, the eNB comprising hardware processingcircuitry configured to: receive, from a User Equipment (UE) operatingin the CE mode, a physical random access channel (PRACH) preamble onPRACH frequency resources allocated for UEs operating in the CE mode;determine, based at least partly on the PRACH frequency resources usedfor the reception of the PRACH preamble, a CE category for the UE from agroup of candidate CE categories; and transmit a Random Access Response(RAR) according to a downlink repetition number that is based at leastpartly on the CE category for the UE.
 21. The eNB according to claim 20,wherein the group of candidate CE categories includes a first and asecond candidate CE category for which PRACH frequency resources for thefirst and second CE categories are exclusive.
 22. The eNB according toclaim 20, wherein: the RAR is transmitted on physical downlink sharedchannel (PDSCH) frequency resources that are based at least partly onthe CE category for the UE; and the PDSCH frequency resources aredisjoint from second PDSCH frequency resources for UEs not operating ina CE mode.
 23. The eNB according to claim 22, the hardware processingcircuitry further configured to transmit a physical downlink controlchannel (PDCCH) data block that includes PDSCH resource allocations forUEs not operating in the CE mode and to refrain from transmission ofPDCCH data blocks for UEs operating in the CE mode.
 24. The eNBaccording to claim 22, the hardware processing circuitry furtherconfigured to transmit a control message that includes an allocation forthe PDSCH frequency resources, a modulation and coding scheme (MCS)indicator for the RAR transmission, and a timing relationship betweenPRACH transmission at the UE and the RAR transmission.
 25. The eNBaccording to claim 20, the hardware processing circuitry furtherconfigured to receive, from the UE, an uplink control message onphysical uplink shared channel (PUSCH) resources according to an uplinkcontrol repetition number.
 26. The eNB according to claim 25, whereinthe uplink control repetition number is based at least partly on the CEcategory for the UE.
 27. The eNB according to claim 25, wherein the RARincludes the uplink control repetition number.
 28. The eNB according toclaim 25, the hardware processing circuitry further configured totransmit, in response to the reception of the uplink control message, acontention resolution message according to the downlink repetitionnumber.
 29. The eNB according to claim 20, wherein: the hardwareprocessing circuitry is further configured to receive, from a second UEnot operating in the CE mode, a second PRACH preamble on second PRACHfrequency resources allocated for UEs that are not operating in the CEmode; and the second PRACH frequency resources are exclusive to thePRACH frequency resources allocated for UEs operating in the CE mode.30. The eNB according to claim 20, wherein the eNB is further to operateaccording to a 3GPP protocol.